Asenapine and its pharmaceutically acceptable salts, including asenapine maleate, are known from U.S. Pat. No. 4,145,434. Asenapine maleate is chemically (3aRS,12bRS)-5-chloro-2-methyl-2,3,3a,12b-tetrahydro-1H-dibenzo [2,3:6,7]oxepino[4,5-c]pyrrole (2Z)-2-butenedioate (1:1), having the structure as represented by Formula I.

Asenapine maleate is marketed in the United States under the brand name SAPHRIS®, for the treatment of schizophrenia.
U.S. Pat. No. 4,145,434 describes a process for the preparation of asenapine by the cyclization of 3-(5-chloro-2-phenoxyphenyl)-1-methylpyrrolidine-2,4-dione (Formula II) to 11-chloro-2-methyl-2,3-dihydro-1H-dibenzo [2,3:6,7] oxepino [4,5-c]pyrrol-1-one (Formula III) using polyphosphoric acid at a temperature of 125° C.

U.S. Pat. No. 7,956,202 describes a process for the preparation of asenapine by the cyclization of the intermediate of Formula II to the intermediate of Formula III using hypophosphoric acid and a catalyst.
The drawbacks associated with the preparation of asenapine by the cyclization of the intermediate of Formula II to the intermediate of Formula III using prior art processes include difficulty in complete removal of phosphoric acid from the reaction mixture. This requires the use of a large amount of water for work-up and also adversely affects the yield at the next step.
Thus, there exists a need in the art for an improved and more efficient process for the cyclization of the intermediate of Formula II to the intermediate of Formula III.